The present invention relates to sheet material for reflecting or decorative use, based upon metal substrates coated for protection against corrosion. Sheet material of the present invention is also capable of being worked into useful shapes, without detrimentally affecting its reflective ability or its anti-corrosion properties.
Many types of lighting fixtures include a metal reflector behind a light source to beam the light in a desired direction and to improve lighting efficiency. Aluminum alloy sheet material is commonly used as such metal reflector because of its ability to maintain a high degree of brightness during use, its formability, and light weight. The brightness of aluminum alloy sheet can be dulled by corrosion in the surrounding atmosphere, by the deposition of fine dust, scratching, and even fingerprints.
In a conventional process for making shaped aluminum alloy reflectors, aluminum alloy sheet is subjected to bright rolling to improve its reflectivity. The bright rolled sheet is then shaped by bending, embossing, or other deformation processes to manufacture reflectors for recessed lighting, downlighting, head lamps, tail lamps, and other reflector applications. The shaped reflectors are typically buffed, chemically brightened, and anodized to improve their resistance to corrosion.
The prior art process described above is costly because anodizing the shaped reflector is an expensive, batch process. Accordingly, there still remains a need for a continuous process of making reflective metal sheet that is capable of being deformed into a desired configuration and maintains its reflective characteristics after it has been protected from corrosion.
A principal objective of the present invention is to provide a process for making reflective metal sheet material that is protected from corrosion, and also deformable without significantly diminishing its resistance to corrosion or its reflective characteristics.
A related objective of the invention is to provide an efficient and economical process for making shaped metal or laminated articles having excellent resistance to corrosion and reflective characteristics.
Additional objectives and advantages of our invention will become apparent to persons skilled in the art from the following detailed description.
In accordance with the present invention, there is provided a process for making a prefinished, deformable reflector sheet. The product is suitable for use in recessed and downlighting applications, in head lamps or tail lamps for motor vehicles, and other drawn or stamped reflector applications.
Metal sheet for making deformable reflector sheet in accordance with the present invention may be made from aluminum alloys or steel. Aluminum alloy sheet is particularly preferred. Suitable forms of steel include mild steel and stainless steel.
The aluminum alloy sheet comprises about 90 wt % or more aluminum together with one or more alloying elements. A particularly preferred alloying element is manganese, comprising about 0.5-1.5 wt % of Aluminum Association 3000 series alloys. Other suitable alloying elements include magnesium, comprising about 0.5-10 wt. % of AA 5000 series alloys; magnesium and silicon, each comprising about 0.5-10 wt % of AA 6000 series alloys; and zinc, comprising about 0.8-8 wt % of AA 7000 series alloys. Suitable tempers for alloys of the AA 5000, 6000, and 7000 series include the H1X, H2X, H3X, and 0 tempers (Aluminum Association designations).
Some particularly preferred AA 3000 series alloys include the AA 3002, 3003, and 3004 alloys, all containing about 1.0-1.5 wt. % manganese.
Some suitable AA 5000 series alloys containing about 0.5-5 wt % magnesium include the AA 5182, 5052, 5657, and 5252 alloys. A preferred AA 5657 alloy sheet has an 0 temper.
Aluminum alloys of the AA 1000 series, containing at least 99 wt. % aluminum, may also be used when excellent workability is desired.
Several particularly preferred embodiments of our invention are described in the following examples.